ZIP Code Radius Search

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description adds behavioral context beyond annotations: it mentions paginated results (up to 500 per page), distance from center in results, and maximum radius values per unit. Annotations already indicate idempotent and read-only, so description complements these with operational details. No contradictions.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise: two sentences, the first front-loading the primary purpose. Every sentence serves a clear role, no fluff.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a tool with 7 parameters and no output schema, the description covers the key aspects: center specification, radius limits, pagination, and result format (code and distance). It could explicitly state that results are sorted by distance, but overall it is sufficiently complete for an agent to use correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with each parameter described. The description adds value by summarizing the two mutually exclusive center options and providing a compact list of max radius per unit, which is not fully captured in individual parameter descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool's purpose: 'Find all ZIP/postal codes within a given radius of a center point.' It specifies the verb 'find', resource 'ZIP/postal codes', and the action 'within a given radius'. It also distinguishes between two center specification methods, making the purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear usage guidelines: it explains how to specify the center (either ZIP+country or lat/long) and includes max radius limits per unit. However, it does not explicitly differentiate this tool from other zipcode-related siblings (e.g., zipcode_distance) or state when to use this vs alternatives.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.